vim. use ledger print as 'formatprg'

You can now try to select some lines using V (visual mode)
and have them automatically formatted using gq

contrib/vim/compiler/ledger.vim

@@ -12,13 +12,9 @@ if exists(":CompilerSet") != 2
   command -nargs=* CompilerSet setlocal <args>
 endif
 
+" default value will be set in ftplugin
 if ! exists("g:ledger_bin") || empty(g:ledger_bin) || ! executable(split(g:ledger_bin, '\s')[0])
-  if executable('ledger')
-    let g:ledger_bin = 'ledger'
-  else
-    echoerr "ledger command not found. Set g:ledger_bin or extend $PATH."
-    finish
-  endif
+  finish
 endif
 
 " %-G throws away blank lines, everything else is assumed to be part of a

contrib/vim/ftplugin/ledger.vim

@@ -12,7 +12,7 @@ let b:did_ftplugin = 1
 
 let b:undo_ftplugin = "setlocal ".
                     \ "foldmethod< foldtext< ".
-                    \ "include< comments< omnifunc< "
+                    \ "include< comments< omnifunc< formatprg<"
 
 " don't fill fold lines --> cleaner look
 setl fillchars="fold: "
@@ -22,6 +22,21 @@ setl include=^!include
 setl comments=b:;
 setl omnifunc=LedgerComplete
 
+" set location of ledger binary for checking and auto-formatting
+if ! exists("g:ledger_bin") || empty(g:ledger_bin) || ! executable(split(g:ledger_bin, '\s')[0])
+  if executable('ledger')
+    let g:ledger_bin = 'ledger'
+  else
+    unlet g:ledger_bin
+    echoerr "ledger command not found. Set g:ledger_bin or extend $PATH ".
+          \ "to enable error checking and auto-formatting."
+  endif
+endif
+
+if exists("g:ledger_bin")
+  exe 'setl formatprg='.substitute(g:ledger_bin, ' ', '\\ ', 'g').'\ -f\ -\ print'
+endif
+
 " You can set a maximal number of columns the fold text (excluding amount)
 " will use by overriding g:ledger_maxwidth in your .vimrc.
 " When maxwidth is zero, the amount will be displayed at the far right side